Control Valve Flow Coefficients

Abstract

The flow coefficient for a control valve is an important hydraulic parameter that is used to select and design the controls for a closed conduit system. The parameter is used to determine flow capacities, valve positioning, and energy losses of the system. The coefficient is also used for the analysis of the flow system for other phenomena such as cavitation and transients. It is important to understand the definition of the flow coefficient, how it is used, and how it is determined for a control valve. At present there are two sets of testing standards to determine the flow coefficient for a valve. The standards are different in the definition of how the coefficient is determined and can result in two different sets of flow coefficient data for a valve. Confusion has resulted in identifying which set of standards was used to generate the valve coefficient information, and the importance of designing a system using the same definition of the coefficient.